Why can't I log into my old yahoo account?

Why i cant post comment to yahoo using my google account? In fact i can log in and with intigration of both?

• Posting comments to yahoo using my Google account

• Answer:

  "... Yahoo to Axe Log-in With Facebook, Google Accounts.. ...YahooYHOO -4.19% will no longer let users sign in using FacebookFB -4.61% and GoogleGOOG -4.67% credentials, a move that will give the company more control over user data, but limiting potential new sign-ups. Visitors to Yahoo sites including Flickr and Fantasy Sports will soon be required to sign in with a Yahoo ID, a spokeswoman for the company said. The change took effect on Monday for users of its college basketball bracket-picking site, and will eventually affect all Yahoo properties, she said. Requiring a Yahoo name and password could help the company collect more data about its 800 million monthly visitors which it can then use to sell more targeted advertising. The company is at a disadvantage to Facebook, which collects information about social connections, and Google, which tracks billions of daily searches by its users. Chief Executive Marissa Mayer has called Yahoo a “personalization company,” and revamped many of the company’s most popular sites to promote news articles and videos to match each user’s tastes and interests. To better control these personalized experiences, Yahoo may need to also control log-ins. “We’re continuing to work on improving the user experience and that does include the sign-in process,” a spokeswoman for Yahoo said. “The intent is to let us offer the best personalized experience for everyone.” Moving all users to Yahoo passwords will also improve security and speed up customer service, she said. But Yahoo risks losing millions of users who won’t bother to register a new account or don’t trust the company to handle their data. The ability to sign in using Facebook, first added to Yahoo sites in 2009, made it easier for new users to sign in without the hassle of creating a new account. The move is also a setback for Facebook and Google, who have expanded their login tools in an attempt to simplify the concept of online identity. The companies give outside developers the login tools for free, and in exchange get data about user activities across a range of sites and mobile apps. Yahoo is one of the largest Web properties to let users log in with their Facebook and Google credentials. The change in policy was earlier reported by Reuters and the tech blog Betanews...." http://blogs.wsj.com/digits/2014/03/05/yahoo-to-axe-log-in-with-facebook-google-accounts/